It is common practice to form holes in wood and metal by a trepaning operation, involving a metal cup in which the edges of the cup are formed with teeth. The cup is mounted on a mandrel and the mandrel, in turn, is mounted in an electric drill. Normally, the cup is deep drawn from a low carbon steel. There are a number of difficulties that have been experienced with these devices, however. First of all, the fact that the cup is formed from low carbon steel means that the teeth are not hard enough to last a long period of time when cutting wood and will not cut metal at all well, except possibly soft metals. It is, of course, not possible to deep draw high carbon steels. Another difficulty experienced is that the machining of the teeth is difficult, since the cup has to be mounted in a special machine for punching the teeth one at a time and grinding must take place in a similar manner. This is a relatively time-consuming operation and, therefore, causes the price of the finished article to be quite high. These and other difficulties experienced with the prior art devices have been obviated in novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a hole saw capable of a long life when used in trepaning operations on wood.
Another object of this invention is the provision of a hole saw capable of cutting metal.
A further object of the present invention is the provision of a hole saw which is relatively easy to manufacture.
It is another object of the instant invention to provide a hole saw formed of a high carbon steel and provided with ground teeth.
A still further object of the invention is the provision of a hole saw which is simple in construction, which is inexpensive to manufacture, and which is capable of a long life of useful service with a minimum of maintenance.
It is a further object of the invention to provide a method for making a hole saw from high carbon steel.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.